Spectrophotometric Method with Silica‐Gel Beads for Determination of Trace Formaldehyde in Air

Abstract

A novel method is described for the determination of formaldehyde, with sensitivity enhancement based on the Hantzsch reaction, which involves the cyclization of ammonium, formaldehyde, and 2,4‐pentanedione (PD) in Nash's reagent to form the yellow compound 3,5‐diacetyl‐1,4‐dihydrolutidine (DDL) at pH 6. Silica‐gel beads are added into solution, and the reaction completes within 55 min at room temperature without heating. The silica‐gel beads not only catalyze the reaction process but also increase the sensitivity of the analysis. The proposed method is simple and convenient. The absorbance at 412 nm is proportional to the concentration of formaldehyde over the range of 0.1–2.0 g · mL−1. The detection limit is 0.1 g · mL−1. This method has been applied to the determination of formaldehyde in air with satisfactory results. This paper was invited as a contribution to a special issue of the journal concerning Chemical Spectroscopy in China. It was presented at Sichuan University, Chengdu China, October 17–24, 2003; the 6th International Symposium on Green Chemistry in China.